1. Field of the Invention
The present invention relates to a system for changing production orders in a corrugation machine which produces corrugated boards cut to different specific widths and lengths according to customers' needs.
2. Related Art
A product specification order change system of a corrugation machine to which the present invention is applicable is shown in FIG. 2. A continuous corrugated board web 3, produced in a preceding portion of the corrugation machine not shown in the figure, enters the order change system portion of the machine at the right hand side of the figure and moves to the left in the direction of the arrows. As described in more detail below, element 2 is a rotary shear section, elements 1a and 1b are slitter-scorer sections, and element 22 is a length cut-off section.
As shown in FIG. 8, a rotary shear 2 comprises a knife cylinder 25 having a knife 24 fixed thereon substantially along the total length thereof, and an anvil cylinder 26 mounted in parallel cooperating relationship with the knife cylinder 25. According to one conventional apparatus, the anvil cylinder 26 has a tapered diametrical shape along its length formed by an elastic body 27 which decreases in thickness from the central portion of the cylinder to a predetermined distance from the peripheral surface thereof. With this construction, the relative phase of the knife cylinder 25 with respect to the anvil cylinder 26 can be changed. By rotating the two cylinders 25 and 26 as the corrugated web 3 passes therethrough, the rotary shear 2 can either cut slits of predetermined length in the edges of the web 3 as shown, or can completely cut the web 3 along its width, as a function of the relative phase set between the cylinders. The rotary shear 2 performs the function of changing over the width setting of the trim 23a, 23b at the edges of the corrugated web so as to produce the desired width W.sub.0 of corrugated sheet product generally designated by numeral 5 in FIG. 8. As shown, a plurality of product sheets 5(A)-5(D) can be produced by the corrugation machine. According to another conventional apparatus, the anvil cylinder 26 has a cylindrical shape along its axis formed by an elastic body 27. The rotary shear 2 can completely cut the web 3 along its width plural times by rotating the cylinders 25 and 26 as the web 3 passes therethrough, creating a gap in the continuous web of sufficient length that a "window" is created, providing sufficient time for the downstream apparatus such as the standby slitter-scorer 1b to switch from standby mode to the in-use mode as shown by 11a. Additionally, the cutoff device 22 can switch over to the next sheet length specification setting.
Next, the function of the slitter-scorer portions 1a-1b of the corrugation machine will be outlined with reference to FIGS. 2 and 8. The slitter-scorers 1a, 1b comprise a pair of upper and lower scorers 28a and 28b and a pair of upper and lower slitter knives 29a and 29b. The scorers 28a and 28b are used to place predetermined score lines on the corrugated web and the slitter knives 29a and 29b are used to form slit grooves in the web such as groove M for dividing the web into separate product sheets and trimming off the trim portions 23a and 23b. Two slitter-scorers 1a and 1b are typically installed along the web running direction to shorten the downtime of the machine required for changing the settings due to a change in product specifications for a new customer order to be processed, with an alternate one of the two slitter-scorers being used for each successive order. The width W of the corrugated board web 3 is set slightly wider than the overall width W.sub.o of the finished product sheets, so that the ends of the web where defects such as deviations in paper adhesion level or paste overflow occur are cut off as waste trim 23a, 23b and disposed of into trim ducts 30a and 30b.
In order to change product sheet specification settings due to an order change, assuming that slitter-scorer 1a is in use, the trim position of the new order to be processed is sent as a signal from a system controller (not shown) to the standby slitter scorer 1b, where the position setting of the trim duct 30b and various settings for the new order are performed. At the same time, on the trim cutting rotary shear 2, the position of the knife 24 and the relative angle of the anvil cylinder 26 with respect to the knife cylinder 25 are set to attain the appropriate cutting length of the widthwise end notches or slits in the ends of the corrugated board web 3. The knife cylinder 25 and the anvil cylinder 26 are then synchronously rotated at predetermined timing intervals as the corrugated board web 3 passes through to form trim cutting notches at desired positions in the web.
As the notch positions reach the standby slitter-scorer 1b, the pair of upper and lower scorers 28b are engaged with the web, and then the pair of upper and lower slitter knives 29b are engaged, by which processing of the new order is performed.
On the other hand, the slitter-scorer 1a processing the old order successively releases the engagement of the upper and lower scorers 28a and the slitter knives 29a at the time that the front edge of the corrugated web of the new order reaches it. Slitter-scorer 1a then assumes a standby state and receives order change settings for the next order. The operations described above function to change only the trim width at the edges of the web according to a product order change in a two-sheet production setting, that is, the system changes from producing product sheets 5(C) and 5(D) to producing product sheets 5(A) and 5(B).
The conventional order change system can stably change product specifications under limited conditions such as where the slit groove M for separating the two sheets is continuous, where the cut lengths of the two sheets are the same even if the slit groove M is discontinuous between orders, or where only one product sheet is produced from the continuous web (not shown).
However, in addition to the width of the product sheets, the cutting lengths L.sub.T and L.sub.D in a two-sheet production are often changed also as shown in FIG. 8. When the desired cutting lengths of the two product sheets are different, the paths of the sheets diverge at a length cutoff section 22 as shown in FIG. 2, so that the sheets are transferred to separate adjustable rotary drum cutoff shears 22a, 22b which cut the sheets to their respective desired lengths.
Therefore, when the product specification is changed, for example, to have different widths as well as different lengths L.sub.T and L.sub.D as shown in FIG. 8, the slit groove M has a discontinuous portion *, which is torn as the sheets diverge at the cutoff section 22 and defective boards are produced. Further, jamming frequently will occur if the defective torn sheet becomes caught in a downstream transfer feed roller.
To solve these problems, a cutting apparatus 31 as shown in FIGS. 9(a) and 9(b) has recently been proposed. This cutting apparatus forms a groove N.sub.o at predetermined central positions in the width direction of the corrugated board web 3, as shown in FIGS. 10 and 11. The central groove N.sub.0 is produced by a knife cylinder 33 having a knife 32 fixed along the width thereof and a pressure plate mechanism 34 having a plurality of individual pressure pistons which selectively divides the corrugated web 3 into a plurality of sections in the width direction, each of which can be raised or lowered independently. The continuous web 3 is interposed between the knife cylinder 33 and the pressure plate mechanism 34 on an endless elastic belt 35 which is driven at predetermined timing intervals. As illustrated in FIGS. 10 and 11, a groove N.sub.0 is formed in the central portion of the continuous web 3 by synchronously rotating the knife cylinder 33 and the elastic belt 35 while grasping the corrugated board web 3 at desired sections with the pressure plate mechanism 34 where the groove N.sub.0 and the edge grooves are to be cut.
The system of FIGS. 9-11 produces a plurality of different kinds of corrugated product sheets having different cut lengths according to particular customer orders. Since a groove N.sub.0 can be formed only at the portions of the web requiring the formation of a groove in the sheet width direction, torn sheets at the specification change point and other faults are eliminated even when the sheet width changes as shown in FIG. 10, as the central groove N.sub.0 provides for continuity of the separation slit groove M between product specification changes for separating the sheets to the upper and lower stage cutoff devices 22a and 22b.
However, when the continuous web 3 is divided into many product sheets 5a-5d as shown in FIG. 11, some sheets such as sheets 5c and 5f are completely cut along their width by the groove N.sub.0. As a result, a sheet with no continuity is created in the TOP sheet group or the DOWN sheet group passing to the cutoff device 22, such that control of the movement of the rear end of the old order sheet 5c and the front end of the new order sheet 5f is lost. Consequently, problems such as zigzag running of the sheets or variations in transfer speed occur. As a result, product sheet specifications such as the cutting length, angle, etc. become erratic, and various malfunctions and defects are caused until the sheet running conditions can be stabilized.
In summary, in a corrugation machine which produces a plurality of different kinds of product sheets from a single continuous web, use of the rotary shear 2 of FIG. 8 causes the position of the slit groove M to become discontinuous at the order change point, causing the sheets to be still connected to each other when sent to separate cutoff length devices at the next stage of the machine. Therefore, the sheets are torn by the vertical separation of the sheet running path to the upper and lower cutoff devices causing defective boards to be produced.
Use of the selective pressure plate mechanism of FIGS. 9-11 forms a central groove N.sub.0 at a predetermined position along the width direction of the continuous web, so that the slit groove M is made continuous between separate product orders, eliminating tearing of a sheet at vertical separation. However, when the groove N.sub.0 in the central portion of the corrugated board web extends across a plurality of product sheets, one or more completely cut sheets will be formed causing sheet transfer control to become unstable with resultant production faults and defects.